\section{Motivation and previous work} \label{theoretical-background}

%\emph{
%First: I don't know if this paragraph is useful; what do you think? it's kind of redundant \\
%Second: Bridging the gap and its advantages. See last phrase: enough for explaining our role? LB: not really, let me work on this when you finish\\
%Third:  Overspecification and previous studies and results.  \\
%\fxnote{SV: I moved a shorter version of the Pechmann paragraph to the intro.. Do you think we have enough theoretical background here?} LB: yes

%	Producing referring expressions plays a central role in human communication: people can only communicate if they agree about the identity of %the object in question. Thus, when children acquire language, one of the first things they learn is how to refer to objects. As a result reference %%has been studied in all academic disciplines that study language and communication. 
%\fxnote{SV: This paragraph may be unnecessary??}


This project is part of a larger effort whose goal is to bridge the gap between psycholinguistics and computational linguistics by studying the production and interpretation of referring expressions \cite{Krahmer-Van-Deemter-2011,Goudbeek_and_Krahmer_2012}. Such a bridge has both theoretical and methodological advantages. Our particular goal is to make psycholinguistic findings more accessible to dialogue system designers. 

\emph{Overspecification} is a topic that has been much studied by psycholinguistics~\cite{Maes_Arts_Noordman_2004}. The findings of psycholinguistic experiments have consistently shown that speakers overspecify about one-third of the time. In an experiment done by Engelhardt et al.~\shortcite{Engelhardt_Bailey_Ferreira_2006}, it was found that while subjects take longer to resolve overspecified references, they do not rate them them any worse than minimal ones. Engelhardt et al. \shortcite{Engelhardt_Bar_11} have shown that electrophysiological measures of brain activity indicate an increased cognitive processing effort when interpreting overspecified descriptions. Our project makes a novel contribution to the area because we are using an experimental approach to study the effect of overspecification on lexical acquisition. 

	\emph{Alignment} is a phenomenon by which speakers adapt and coordinate with each other, which can range anywhere from using the same vocabulary to referring to objects with the same REs. Brennan and Clark \shortcite{Brennan_Clark_1996} called this phenomenon \emph{conceptual pacts} and observed it in situations where two or more speakers had to refer to the same object, when they started referring to the objects using the same vocabulary and level of detail. 
	In practical terms, lexical acquisition can be seen as the most extreme case of alignment.  In the cases when a speaker is learning a new language, they are completely \emph{aligned} with their mentor. The learner uses the same vocabulary and grammatical constructions as their teacher because they have an extremely limited choice of linguistic resources that they can use \cite{Atkinson_Churchill_Nishino_Okada_2007}. In other cases of dialogue, it is more difficult to isolate alignment because it is hard to tell where a speaker's speech resources stem from and to which extent they are aligning themselves with their interlocutor. While studies have shown that alignment exists not only during language learning \cite{Goudbeek_and_Krahmer_2012}, we decided to perform our study using lexical acquisition as its focus, to control the speaker's knowledge of the language and target the 'square one' from where alignment starts. To the best of our knowledge, there are no studies on the effect of overspecification on language acquisition. 


%\fxnote{FL: Compte tenu des thematiques de la soumission,  j'attendais un 2.2. Conceptual pacts qui decrive un peu plus la notion de Brennan and Clark et qui montre l'apport que peut constituer  le travail presente ici}
%\fxnote{SV: Do you think that what we did in the paragraph on alignment is enough?}

